class Solution
{
public:
    ListNode* trainningPlan(ListNode* l1, ListNode* l2)
    {
        ListNode* dum = new ListNode(0);
        ListNode* cur = dum;
        while (l1 != nullptr && l2 != nullptr)
        {
            if (l1->val < l2->val)
            {
                cur->next = l1;
                l1 = l1->next;
            }
            else
            {
                cur->next = l2;
                l2 = l2->next;
            }
            cur = cur->next;
        }
        cur->next = l1 != nullptr ? l1 : l2;
        return dum->next;
    }
};